Enhance API endpoints with response type annotations

- Updated various API endpoints to include response type annotations using .Produces<T>() for better documentation and type safety.
- Enhanced activation, admin, user, config, and other endpoints to specify response types, improving clarity for frontend integration.
- Added new DTOs for structured responses in authentication and Telegram-related endpoints.
- Improved overall API schema generation to reflect these changes, ensuring consistency between backend and frontend types.

backend/src/PnvPanel.Api/Endpoints/AdminStatsEndpoints.cs

@@ -2,6 +2,7 @@ using PnvPanel.Api.Common;
 using PnvPanel.Application.Admin.Audit;
 using PnvPanel.Application.Admin.Stats;
 using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
 using PnvPanel.Infrastructure.Identity;
 
 namespace PnvPanel.Api.Endpoints;
@@ -14,8 +15,8 @@ public static class AdminStatsEndpoints
             .WithTags("Admin.Stats")
             .RequireAuthorization(policy => policy.RequireRole(RoleNames.Admin));
 
-        admin.MapGet("/stats", GetStats);
-        admin.MapGet("/audit", GetAudit);
+        admin.MapGet("/stats", GetStats).Produces<StatsDto>();
+        admin.MapGet("/audit", GetAudit).Produces<PagedList<AuditLogDto>>();
 
         return app;
     }